Two cm of spinal cord will be radiated with 20 or 40 Gy of radiation and the animals will be followed until predetermined times from 2hr to 360 d or until they develop neurologic symptoms, whichever is first. At these times MRI of the spinal cord, laminectomy, direct Doppler blood flow and EPR oximetry with implanted LiPc crystals will be done and the animal will be sacrificed for histologic study and cytokine assay. The effect of intrathecal radiation protectors will be assessed.